1. Field of the Invention
The invention relates to backlighting and more particularly to such a backlight module including a white reflective film having plasma formed thereon, and an illumination unit having light-emitting diodes (LEDs) as light source, and the white reflective film being bent to conceal a light guide plate so that emitted light can be reflected by the bent white reflective film, and it can make the backlight module thinner and simplify the manufacturing processes.
2. Description of Related Art
Membranes are applicable to calculators, electronic scales, computer and keyboards having keys and integrated circuits (ICs). Printed circuit board for the membrane employs plasma as conductive material which is printed on substrate formed of polyethylene terephthalate (PET) by lithography. Next, the half-finished product is sent to a heater to heat for more than one hour in a temperature of 150-250° C. for curing. The employed plasma is typically heating-type plasma which adheres to other elements when temperature reaches about 150° C. However, the membrane may malfunction and have poor conductibility after such long period time of heating.
Typically, a backlight module and the membrane are provided in a keyboard so that a user can operate the keyboard under poor lighting conditions. The backlight module comprises a reflective plate, a transparent light guide plate disposed on the reflective plate for guiding light and allowing light to pass through, and a light emitting arrangement for emitting light toward the light guide plate. The light is reflected by the reflective plate and is guided by the light guide plate, thereby uniformly directing the light along the light guide plate. The membranes are disposed on the light guide plate. The membranes are formed of transparent material. Thus, a blocking layer (e.g., dark ink or opaque material) in an opaque area is provided to restricted the light only emmited through desired areas.
The light emitting arrangement is provided at one side of the light guide plate. Thus, distal portions of the light guide plate are insufficiently illuminated. Further, the stack construction of the conventional backlight module is relatively thick and its manufacturing process is complicated. Furthermore, the optical passage is formed by the transparent membranes made of PET and the light guide plate made of optical polycarbonate (PC). Silver Ink is provided in the circuit of the membranes for adhering purpose. However, the silver ink can absorb light. Thus, light passing the optical passage may have its strength decreased greatly due to the absorption. As a result, illumination is poor. Thus, the need for improvement still exists.